This is a fusion peptide containing amino acids 71 to 89 fragment of the Bak BH3 domain fused to antennapedia peptide. The Bcl-2 homology 3 (BH3) domain is crucial for the death-inducing and dimerization properties of pro-apoptotic members of the Bcl-2 protein family, including Bak, Bax, and Bad. Synthetic peptides corresponding to the BH3 domain of Bak bind to Bcl-xL, antagonize its anti-apoptotic function, and rapidly induce apoptosis when delivered into intact cells via fusion to the antennapedia homeoprotein internalization domain.